In engineering, a mechanism is a device that transforms input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components that can include: * Gears and gear trains * Belt and chain drives * Cam and followers * Linkage * Friction devices, such as brakes and clutches * Structural components such as a frame, fasteners, bearings, springs, lubricants * Various machine elements, such as splines, pins, and keys. The German scientist Reuleaux provides the definition "a machine is a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion." In this context, his use of machine is generally interpreted to mean mechanism. The combination of force and movement defines power, and a mechanism manages power to achieve a desired set of forces and movement. A mechanism is usually a piece of a larger process or mechanical system. Sometimes an entire machine may be referred to as a mechanism. Examples are the steering mechanism in a car, or the winding mechanism of a wristwatch.Multiple mechanisms are machines.